var _system = {
    $: function (id) {
        return document.getElementById(id);
    },
    _client: function () {
        return {
            w: document.documentElement.scrollWidth,
            h: document.documentElement.scrollHeight,
            bw: document.documentElement.clientWidth,
            bh: document.documentElement.clientHeight
        };
    },
    _scroll: function () {
        return {
            x: document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft,
            y: document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop
        };
    },
    _cover: function (show) {
        if (show) {
            this.$("cover").style.display = "block";
            this.$("cover").style.width = (this._client().bw > this._client().w ? this._client().bw : this._client().w) + "px";
            this.$("cover").style.height = (this._client().bh > this._client().h ? this._client().bh : this._client().h) + "px";
        } else {
            this.$("cover").style.display = "none";
        }
    },
    _guide: function (click) {
        this._cover(true);
        this.$("guide").style.display = "block";
        this.$("guide").style.top = (_system._scroll().y + 5) + "px";
        window.onresize = function () {
            _system._cover(true);
            _system.$("guide").style.top = (_system._scroll().y + 5) + "px";
        };
        if (click) {
            _system.$("cover").onclick = function () {
                _system._cover();
                _system.$("guide").style.display = "none";
                _system.$("cover").onclick = null;
                window.onresize = null;
            };
        }
    },
    _zero: function (n) {
        return n < 0 ? 0 : n;
    }
};
 